Biphenylenes. Part XXVI. Reactions of 2,3,6,7-tetramethoxy-1,8-dimethylbiphenylene and of 6,7-dimethoxy-1,8-dimethylbiphenylene-2,3-quinone

Abstract

Attempted bromination and nitration (in acetic anhydride) of 2,3,6,7-tetramethoxy-1,8-dimethylbiphenylene leads in each case to the formation of 6,7-dimethoxy-1,8-dimethylbiphenylene-2,3-quinone as the major product. The quinone is also obtained on oxidation of the biphenylene with chromium trioxide and in low yield on treatment with aluminium bromide. Treatment of the biphenylene with cold concentrated nitric acid gives 6,7-dimethoxy-1,8-dimethyl-4-nitrobiphenylene-2,3-quinone.

The mono-oxime of 6,7-dimethoxy-1,8-dimethylbiphenylene-2,3-quinone undergoes a second-order Beckmann rearrangement to give a derivative of benzocyclobutene.

Treatment of 6,7-dimethoxy-1,8-dimethylbiphenylene-2,3-quinone with ethylenediamine gives a derivative of the new ring system, benzo[3,4]cyclobuta[1,2-g]quinoxaline.

The preparation of 4,5-dimethylbiphenyleno[2,3-c]furazan-6,7-quinone and 6,7-dimethylbenzo[3,4]cyclobuta[1,2-b]phenazine-8,9-quinone, each of which may be regarded as a derivative of biphenylene-2,3:6,7-diquinone, is described.